HadoopHDFSJava编程

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.net.URI;

import org.apache.commons.io.IOUtils;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.fs.FSDataInputStream;

import org.apache.hadoop.fs.FSDataOutputStream;

import org.apache.hadoop.fs.FileStatus;

import org.apache.hadoop.fs.FileSystem;

import org.apache.hadoop.fs.LocatedFileStatus;

import org.apache.hadoop.fs.Path;

import org.apache.hadoop.fs.RemoteIterator;

import org.junit.Before;

import org.junit.Test;

/**

 * HDFS java编程

 * 一般用hdfs shell 来操作,如下：

 * hadoop fs -put aa.txt /

 * hadoop fs -get /aa.txt

 * hadoop fs -ls / 

 * hadoop fs -cat /aa.txt

 *

 */

public class HdfsUtil {

FileSystem fs = null;

@Before

public void init() throws Exception{

//读取classpath下的xxx-site.xml 配置文件，并解析其内容，封装到conf对象中

Configuration cOnf= new Configuration();

//也可以在代码中对conf中的配置信息进行手动设置，会覆盖掉配置文件中的读取的值

conf.set("fs.defaultFS", "hdfs://node1:9000/");

//根据配置信息，去获取一个具体文件系统的客户端操作实例对象

fs = FileSystem.get(new URI("hdfs://node1:9000/"),conf,"username");

}

/**

* 上传文件，比较底层的写法

* 

* @throws Exception

*/

@Test

public void upload() throws Exception {

Configuration cOnf= new Configuration();

conf.set("fs.defaultFS", "hdfs://node1:9000/");

FileSystem fs = FileSystem.get(new URI("hdfs://node1:9000/"),conf,"username");

Path dst = new Path("hdfs://node1:9000/aa/aa2.txt");

FSDataOutputStream os = fs.create(dst);

FileInputStream is = new FileInputStream("d:/aa.txt");

IOUtils.copy(is, os);

}

/**

* 上传文件，封装好的写法

* @throws Exception

* @throws IOException

*/

@Test

public void upload2() throws Exception, IOException{

fs.copyFromLocalFile(new Path("d:/aa.txt"), new Path("hdfs://node1:9000/bb.txt"));

}

/**

* 下载文件

* @throws Exception 

* @throws IllegalArgumentException 

*/

@Test

public void download() throws Exception {

fs.copyToLocalFile(new Path("hdfs://node1:9000/aa/bb.txt"), new Path("d:/aa_down.txt"));

}

/**

* 查看文件信息

* @throws IOException 

* @throws IllegalArgumentException 

* @throws FileNotFoundException 

* 

*/

@Test

public void listFiles() throws FileNotFoundException, IllegalArgumentException, IOException {

// listFiles列出的是文件信息，而且提供递归遍历

RemoteIterator files = fs.listFiles(new Path("/"), true);

while(files.hasNext()){

LocatedFileStatus file = files.next();

Path filePath = file.getPath();

String fileName = filePath.getName();

System.out.println(fileName);

}

System.out.println("---------------------------------");

//listStatus 可以列出文件和文件夹的信息，但是不提供自带的递归遍历

FileStatus[] listStatus = fs.listStatus(new Path("/"));

for(FileStatus status: listStatus){

String name = status.getPath().getName();

System.out.println(name + (status.isDirectory()?" is dir":" is file"));

}

}

/**

* 创建文件夹

* @throws Exception 

* @throws IllegalArgumentException 

*/

@Test

public void mkdir() throws IllegalArgumentException, Exception {

fs.mkdirs(new Path("/aaa/bbb/ccc"));

}

/**

* 删除文件或文件夹

* @throws IOException 

* @throws IllegalArgumentException 

*/

@Test

public void rm() throws IllegalArgumentException, IOException {

fs.delete(new Path("/aa"), true);

}

public static void main(String[] args) throws Exception {

Configuration cOnf= new Configuration();

conf.set("fs.defaultFS", "hdfs://node1:9000/");

FileSystem fs = FileSystem.get(conf);

FSDataInputStream is = fs.open(new Path("/jdk-7u65-linux-i586.tar.gz"));

FileOutputStream os = new FileOutputStream("c:/jdk7.tgz");

IOUtils.copy(is, os);

}

}

Hadoop HDFS Java编程